Browsing by Author "Chang, Chin-Yen"

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Donor-acceptor polymers based on multi-fused heptacyclic structures: synthesis, characterization and photovoltaic applications
(2010)
Wu, Jhong-Sian
;
Cheng, Yen-Ju
;
Dubosc, Martin
;
Hsieh, Chao-Hsiang
;
Chang, Chin-Yen
We report here two novel 2,7-fluorene- and 2,7-carbazole-based conjugated polymers PFDCTBT and PCDCTBT containing ladder-type heptacyclic structures with forced planarity. PCDTBT shows excellent solubility, low band gap and high hole mobility, leading to a power conversion efficiency of 3.7%.
Hierarchical Superstructures with Control of Helicity from the Self-Assembly of Chiral Bent-Core Molecules
(2012-07-01)
Lin, Shih-Chieh
;
Ho, Rong-Ming
;
Chang, Chin-Yen
;
Hsu, Chain-Shu
;
應用化學系
"Herein, two asymmetric chiral bent-core molecules, 3-[(4-{[4-(heptyloxy)benzoyl]oxy}benzoyl)oxy]-phenyl-4-[(4-{[(1R)-1-methylheptyl]oxy}benzoyl)oxy] benzoate (BC7R) and 3-[(4-{[4-(heptyloxy)benzoyl]oxy}benzoyl)oxy]-phenyl-4-[(4-{[(1S)-1-methylheptyl]oxy}benzoyl)oxy] benzoate (BC7S), were synthesized to demonstrate control of the helicity of their self-assembled hierarchical superstructures. Mirror-imaged CD spectra showed a split-type Cotton effect after the formation of self-assembled aggregates of BC7R and BC7S, thereby suggesting the formation of intermolecular exciton couplets with opposite optical activities. Both twisted and helical ribbons with preferential helicity that corresponded to the twisting character of the intermolecular exciton couplet were found in the aggregates. The formation of helical ribbons was attributed to the merging of twisted ribbons through an increase in width to improve morphological stability. As a result, control of the helicity of hierarchical superstructures from the self-assembly of bent-core molecules could be achieved by taking advantage of the transfer of chiral information from the molecular level onto the hierarchical scale."
Hierarchical Superstructures with Helical Sense in Self-Assembled Achiral Banana-Shaped Liquid Crystalline Molecules
(2008-11-10)
Lin, Shih-Chieh
;
Lin, Tz-Feng
;
Ho, Rong-Ming
;
Chang, Chin-Yen
;
Hsu, Chain-Shu
The self-assembly of 1,3-phenylene bis[4-(4-n-heptyloxybenzoyloxy)-benzoates] (BC7) is studied to examine the formation of helical morphologies from achiral banana-shaped liquid crystal molecules at different self-assembling levels. Various hierarchical superstructures including flat-elongated lamellar crystal, left- and right-handed helical ribbons, and tubular texture are observed while the BC7 molecules self-assemble in THF/H(2)O solution. By contrast, only plate-like morphology is observed in the self-assembly of achiral linear shaped 1,4-phenylene bis[4-(4-n-heptyloxybenzoyloxy)-benzoates] (LC7) molecules, indicating that the chirality of the self-assembled texture is strongly dependent upon the molecular geometry of the achiral molecules. The formation of the helical superstructures, namely hierarchical chirality, is attributed to the conformational chirality from the achiral banana-shaped liquid crystalline molecules, as evidenced by significant optical activity in time-resolved circular dichroism experiments. Selective area electron diffraction is performed to examine the structural packing of the hierarchical superstructures. As observed, the molecular disposition of the lamellar crystal is identical to that of the helical superstructure. Also, the diffraction patterns of the helical superstructures appeared arc-like patterns consisting of a series of reflections, suggesting that the helical morphology resulted from the curving of the lamellar crystals through a twisting and bending mechanism. Consequently, the model of molecular disposition in the self-assembled helical superstructures from the achiral banana-shaped molecules is proposed. The morphological evolution in this study may provide further understanding with respect to the chiral information transfer mechanism from specific molecular geometry to hierarchical chirality in the achiral banana-shaped molecules.
High birefringence lateral difluoro phenyl tolane liquid crystals
(2010)
Song, Qiong
;
Gauza, Sebastian
;
Xianyu, Haiqing
;
Wu, Shin Tson
;
Liao, Yung-Ming
Four laterally difluorinated phenyl tolane liquid crystals were synthesised and their physical properties evaluated. These compounds exhibit a fairly small heat fusion enthalpy (Delta H similar to 12.56 kJ mol(-1)), which is favourable for mixture formulations. For comparison, four lateral difluoro cyclohexane tolane homologues are also studied. We doped 10 wt% of each compound into a commercial negative mixture N1 and measured the birefringence, visco-elastic coefficient and figure of merit. Birefringence varies very little between homologues, but the visco-elastic coefficient increases as alkyl chain length increases. The refractive indices of these guest-host mixtures at 1550 nm are also measured.
Synthesis and mesomorphic properties of -methylstilbene-based liquid crystals
(2009)
Chang, Chin-Yen
;
Ho, Kang-Wei
;
Hsu, Chain-Shu
;
Lin, Chih-Hung
;
Gauza, Sebastian
Six series of -methylstilbene-based liquid crystals, i.e. 4-(4-alkylphenyl)-4'-amino--methylstilbenes (2a-e), 4-(4-alkylphenyl)-4'-cyano--methylstilbenes (3a-e), 4-(4-alkylphenyl)-4'-isothiocyanato--methylstilbenes (4a-e), 4'-(trans-4-alkylcyclohexyl)-4-fluoro--methylstilbenes (5a-e), 4'-(trans-4-alkylcyclohexyl)-4-amino--methylstilbenes (7a-e) and 4'-(trans-4-alkylcyclohexyl)-4-isothiocyanato--methylstilbenes (8a-e) were synthesised. All of these -methylstilbene-based compounds exhibit an enantiotropic nematic phase. Some of the 4-(4-alkylphenyl)-4'-isothiocyanato--methylstilbenes with longer alkyl chains exhibit a smectic A phase. All of the liquid crystals obtained exhibit a wide nematic range and high birefringence of 0.16-0.46. Both series of isothiocyanato-based, liquid crystal compounds 4a-e and 8a-e containing -methylstilbenes revealed much lower melting points and clearing temperatures than their cyano and amino homologues.
Synthesis of laterally substituted alpha-methylstilbene-tolane liquid crystals
(2008)
Chang, Chin-Yen
;
Chien, Szu-Yuan
;
Hsu, Chain-Shu
;
Gauza, Sebastian
;
Wu, Shin-Tson
Three series of alpha-methylstilbene-tolane liquid crystals, 4-[2-(4-alkylphenyl)-1-ethynyl]-4'-fluoro-alpha-methylstilbene (3a-3e), 4-[2-(4-alkylphenyl)-1-ethynyl]-2'-methyl-4'-fluoro-alpha-methylstilbene (4a-4e) and 4-[2-(4-alkylphenyl)-1-ethynyl]-3'-methyl-4'-fluoro-alpha-methylstilbene (5a-5e), were synthesized and their phase transition temperatures characterized. All the alpha-methylstilbene-tolane liquid crystals exhibit an enantiotropic nematic phase. Compounds 5a-5e, which contain a lateral methyl group at the 3 position of the middle phenyl ring, display low melting points, a wide nematic range and a small enthalpy of fusion. Their potential applications for displays and laser-beam steering are noted.